The incandescent lamps used in automotive reflectors are fixed into the envelope of reflectors as replaceable lamp assemblies in such a way that the reflector and the lamp form a closed unit in which a sealing prevents humidity or dust from penetrating into the reflector. The incandescent lamp is equipped with locking elements constituting detachable joints with the elements formed in the wall of the reflector. The envelope of the incandescent lamp is set inside the reflector, while the terminals providing connection to the electrical circuit of the automobile are set outside of the reflector. The incandescent lamp must be fixed in the reflector so that the filament of the incandescent lamp takes a precisely defined position in the reflector-envelope, otherwise the beam of rays would deviate from the applicable standards. The incandescent lamp must keep this optical position during the operation, that is impacts and vibrations of the automobile must not dislocate the lamp from its position described above. At the same time, the fixing must be detachable so that the incandescent lamp can be replaced in the event of its defect. According to the effective IEC Standard No. 60061-2, the fixing is accomplished with a springy locking element pressing the incandescent lamp into the so-called V-supports shaped in the wall of the reflector by at least 10 N force. The locking element is simultaneously wedged in an indent shaped in the wall of the reflector.
An incandescent lamp applicable in automotive reflectors is described in PCT published patent application No. WO 97/25733. This lamp has a plastic base, a metal support portion and a metal support sleeve. The lower part of the metal support portion is attached to the metal support sleeve while its upper part is fixing the envelope of the incandescent lamp. The lower part of the metal support sleeve is embedded in the plastic base and the upper part of the sleeve is equipped with optical flanges. The filament of the lamp is connected through lead-out wires to terminals which can be connected to the electrical circuit of the automobile. The incandescent lamp is fixed in the reflector by placing the lamp in the opening at the rear end of the reflector, while the optical flanges penetrate into the grooves shaped in the opening of the reflector and designed to match these optical flanges. Then the lamp is twisted around its longitudinal axis while the incandescent lamp is fixed in the reflector. Fixing is provided for by a compression spring which, in one of the embodiments, is welded to the outer wall of the metal support sleeve with one end, while the other end is resting free on the outer wall of the metal support sleeve. The middle of the compression spring constitutes a flare resting on the rim of the opening of the reflector when the lamp is twisted in the reflector.
In an other embodiment, the compression spring is designed as a flaring leafspring, but its ends are placed into the apertures between the metal support sleeve and the plastic base. The flaring portion of the leaf-spring protrudes outside of the outer wall of the metal support sleeve. When the flaring portion of the leaf-spring is compressed in the course of fixing the incandescent lamp in the reflector, the ends of the leaf-spring slide deeper into the apertures, while the flaring part abuts along the opening of the reflector as described above.
In a further configuration, the flaring leaf-spring protrudes through a breach formed in the wall of the metal support sleeve under one of the three optical flanges. The ends of the leaf-spring rest on the bumpers designed on the metal support sleeve and the plastic base so that the leaf spring is compressed between these two bumpers also designed as supports.
In all the above three cases, the compression spring is made from spring steel as a separate component, which must be bent to provide the required shape, and it reaches the final position while rubbing on the glass wall of the opening of the reflector when the lamp is fixed in the reflector. Each of the presented characteristics has some kind of disadvantage. Managing the compression spring as a separate component requires separate assembling and separate storage of components. Bending the spring steel to provide the required shape is a further process increasing the manufacturing costs. The rubbing motion in the course of fixing results in the scratching of the reflector, dislocation of its reflecting surface and consequently in the decrease of the projected light.